The subject of the present invention is a multilayer anti-drumming and stiffening sheeting, characterized in that it comprises a previously known anti-drumming layer integrally connected with a stiffening layer made from a matrix drenched with a thermosetting plastic.
The multilayer anti-drumming and stiffening sheeting serves in particular to simultaneously deaden and stiffen slightly curved, or flat metal sheets.
In many fields of technology, e.g., in automotive engineering or when fabricating household utensils, thin-walled metal sheets are employed which are caused to vibrate and, thereby, to radiate sound due to moving parts, e.g., running engines. To control and reduce this sound radiation, said metal sheets have heretofore been provided with anti-drumming linings, which dampen the vibrations and thereby reduce the sound.
These previously known anti-drumming linings consist of filled and unfilled bituminous materials or filled or unfilled plastic materials comprising the following plastics mentioned by way of example: polymethacrylic acid esters, polyvinyl chloride, polyisobutylene, nitrile rubber, polyester, natural rubber, polyvinyl acetate, polystyrene, and polymethylmethacrylate.
The following fillers are also mentioned by way of example: limestone flour, mica, asbestos, and slate flour.
The use of these anti-drumming linings reduces the sound radiated by the metal sheets into the ambient air. Apart from these vibrations, slightly curved metal sheets are also subject to sudden "snapping" sounds. Such snapping sounds may be produced when slightly curved surfaces are loaded with a force from the convex side so that the sheet, when a given force is exceeded, curves inwardly under impact stress with a loud cranking sound while passing through an unsteady intermediate position.
Removal of this force generally causes the curved surface to spring back spontaneously to its initial position with a corresponding cracking sound. In industry, e.g., in automotive engineering, the occurrence of this snapping effect is generally avoided by appropriate treatment of the metal sheet. For example, the sheet metal may be formed or corrugated. Another way of avoiding the snapping effect is to provide stiffening ridges.